Reversible thermostatic control system



Feb. 28, 1939. H, R, CRAGO 2,149,085

REVERSIBLE THERMOSTATIC CONTROL SYSTEM Filed MarCh 21, 1936 Iwentor:Havjry Rva o,

Patented Feb. 28, 1939 UNITED STATES PATENT OFFICE REVERSIBLETHEnMosTA'rIc CONTROL SYSTEM Harry R. Crago, Caldwell, N. J., assignerto General Electric Company, a corporation of New York My inventionrelates to a reversible thermostatic control system.

An object of my invention is to provide an improved thermostatic controlsystem that 'can be used for control of both heating and cooling in yearround air conditioning service.

Heretofore it has been the practice to manuallyl change the setting of acontrol thermostat so that in the summertime, when the space to beconditioned is cooled, the temperature therein would be maintained at ahigher value than it would be in the winter time when the space wasbeing heated. Manual operations are also required to change over fromsummer to winter control in l5 the widely used central duct systemswherein individual room thermostats control the operation of dampers toregulate the :dow of the heat exchange medium through branch ducts tothe rooms. In this type of system it is necessary to 20 reverseconnections between the control thermostat and the damper actuatingmeans so that the latter will open the damper in the winter time toallow the ow of heated medium when the temperature decreases below apredetermined minimum and in the summertime to allow the flow of cooledmedium when the temperature rises above a predetermined maximum.

The present invention is an improvement of the inventions on whichapplications for Letters 30 Patent were iiled as follows: Serial No.'10,100 andSerial No. 70,099, both led March 21, 1936, and assigned tothe assignee of the present application. In the rst of theseapplications there is disclosed a system utilizing a centrally locatedthermostat` adapted to reverse the connections of thermostats located inthe respective rooms to which the heat exchange medium is` supplied. Inthe latter there is disclosed an improved form oi' device in which aunitary device comprising three 40 thermal responsive means areutilized.

It is an object of my invention to. provide a simplified control inwhich a unitary device inv which only two` thermal responsive means arerequired.

45 A further object of my invention is to. provide means whereby theranges in which thermostatsV 5o A more detailed understanding of thepresent invention may be secured from the following' description takenin connection with the accompanying drawing in which is illustrated apreferred embodiment of=the invention. Ii'lg. 1 oi A55* the drawingillustrates a schematic diagram. partially in sectional elevation, of aconditioning system embodying my invention; Fig. 2 discloses a plan viewof one form of my unitary thermostatic control device provided withmeans for preventing the thermal responsive means from operating 5 inoverlapping" ranges, and Fig. 3 discloses apartial perspective view ofFig. 2.

The air conditioner Ill illustrated in the drawing may be of anyconventional type but for purpose of illustration I have chosen thewell-known l0 type using a. motor driven compressor for providingrefrigeration and other means for heati'ng and humidifying the air, aswill be briefly described hereinafter. The conditioner is supplied withair through an inlet passage II extending without the walls of theconditioner proper. This supply of air may be either fresh air or amixture of fresh and recirculated air and since both methods ofsupplying air to the conditioner are well-known to Vthose skilled .inthe art I have not illustrated them. rlZhe supply of air is forcedthrough the conditioner by means of a fan I2 driven by means of anelectric motor I3. 'I'he motor may be supplied with energy from anysuitable source (not shown) and may be energized constantly orintermittently as desired. 'Ihe air is heated by means of a coil I4supplied with steam from any suitable source through conduits I5, theinlet conduit being provided with any well-known type of solenoidoperated valve I6. After passing by the heater the air is humidiiied byany desirable humidifying means illustrated by reference numeral Ilsupplied with water through conduits I8. Thereafter the air passes by anevaporator I9 forming part oi' a familiar 35 type of cooling systemindicated generally by reference numeral 20. Y 1 The cooling systemcomprises a` compressor 2| driven bymeans of an electric motor 22supplied with energy` from a suitable source in a manner to be describedhereinafter. The compressed refrigerant passes through condenser coils23 adaptedto be cooled in any well-known manner (cooling means notshown). The condensed refrigerant is collected in the liquid receiver 2land 45 from thence the liquid passes to the evaporator. I9 throughconduit 25 under the control of the refrigerant valve 26 which is inturn controlled by the usual thermostatic bulb 21. After passing throughthe evaporator I9 the gaseous refrigerant 5o passes to the compressorf2lthrough a conduit 28.

The air, after being conditioned, is circulatedto any desired space suchas a room, zone, or building which itis desired to condition, through acentral duct III having individual branch ducts 3| 55 and 32 leading tothe separate spaces 55 and 95, respectively.

The regulation of the flow of conditioned air to the various spaces,of'which I have illustrated but two, is under the control of dampers 55positioned in each of the individual air ductsleading to the variousspaces or rooms. The dampers are connected by means of crank arms Statoactuating means indicated generally by reference numerals 3l, whichactuating means will be described more in detail hereinafter. Theactuating means are in turn controlled by means of my improvedthermostatic control systems, indicated generally at 58, positioned inthe spaces to be conditioned. The thermostatic system is adapted tomaintain the temperature of the rooms within a predetermined range inwinter and a second predetermined range in summer in a manner valso tobe described more fully hereinafter.

The reversible thermostatic system positioned within the room` consistsof two thermal responsive elements, which I have illustrated as being ofthe well-known bimetallic type, indicated by reference numerals 39 and459. These bimetallic elements are so positioned that they move towardthe right as illustrated in Fig. l in response to a decrease intemperature. Consequently, the right-hand contact of the pair ofcontacts associated with veach of elements 39 and lili, may be termedthe low and the opposite contact, the high contact. The high contact ofthermostat 59 is connected tol thermal responsive element 59 by means ofconductor di. The low contact associated with element 39 is connectedwith the high contact associated with element @9' through conductor 92and these are in turn connected by conductor 63 to the secondary windingof a transformer 59 through which the thermostatic system is providedwith energy from a suitable source 95. 'I'he'other terminal of thesecondary winding of transformer d is connected to the. low contactassociated with element 69 by means of a conductor d6. It may be seenthat if temperature conditions within the space 3ft are such as toposition the thermal responsive elements in the positions shown thenthey short circuit the relay il through conductors 46 and a conductor 58leading from one terminal of the relay to element 39. It may be seenfurther that relay Ail' will be energizedfif element 39 moves intoengagement with its low contact on a decrease in temperature below apredetermined value or upon engagement of element 59 with its high-contact upon an increase in temperature. Upon energization of relay dlla holding circuit is established therefor bythe closure of contacts 59and 59 by bridging mer. ber 5l. e

Associated with the relay dll is a second fswitch member 52 adapted tocontrol the operation of the damper actuating means in a manner thatwill now be described. The damper 35 is connected by means of a crankarm 36 to the actuating means 5l comprising an electrical motor .53adapted to receive energy from the supply d5 through a transformer 55.The energization f motor 53 to open and close the damper is effected bymeans of the switch element 52 and its cooperating contacts 55 and 56 inconjunction with a limit switch mechanism comprising cam 51 and movableswitch members 58 and 59. Engagement of switch member52 with contact 56upon energization of relay 4l com'pletes a. circuit from contact 5Ethrough conductor 6l, motor 53, secondary winding of transformer 54,conductors 62 and 63, limit switch 59 and conductor 64 to arcanes switchmember 52. Motor 59 thereupon operates to open damper 5,5 by means of acrank arm ,'56 while at the same time cam 5l is rotated. At the timedamper 35 is in its fully open position the cam 5l is rotated 180 toopen limit switch 5 59 and close limit switch 58 thereby deenergizingmotor 53. Upon subsequent movement of switch member 52 from contact 56to contact 55 upon deenergization of relay ll'L'a circuit is establishedfrom contact 55 through conductors 65 and 62,910 secondary winding of4transformer 55, motor 53,

, conductor 5i, limit switch 58 and conductor 54 to switch member 52,thereby energizing motor 53 to return damper 35 to its closed position.Cam

5l again rotates 180 opening limit switch 58 to l5 deenergize motor 53and closing limit switch 59 preparatory to the next energization ofrelay lll.

It will be understood that other well-known forms of control dampers maybe employed if desired. This is particularly true if modulated 20control of damper 35 is desired and if such modulated control is deemedto be desirable the damper operatingv motor and control described may bemodied in the manner shown in Letters Patent No. 1,902,327, chester I.Hau, also assigned to 25 v the assignee of the present application. l

In order selectively to obtain eitherheating or cooling of the airpassing through the conditioner, I have provided a control indicatedgenerally at 55. The control is energized-through a trans- 30 former 66connected to the source of power d5. A relay 6l is under the control ofa thermal responsive device 68 suitably located at some central point ofthe building so as to be responsive to average temperature conditions. nWhen the 35 relay is deenergized under low temperature conditions, asindicated by Fig. 1, the air passing through the conditioneris heatedand when the relay is energized the heating means is renderedineffective and the cooling means is placed 4in 40 operation. The relayoperates a pair of switches 69 and 19, the former adapted to close aholding circuit for the relay and the latter controlling the operationof the heating and cooling means. Thus, as indicated in the figure,switch 19 is 45 in its lower position thereby energizing a solenoid vtoopen the valve i6 through a circuit.that is as follows: from thesecondary winding of transformer 66 through conductor li, switch l0, andconductor 'l2 to the valve operating solenoid i4, 50 and from thenceback to the secondary winding through conductors 'l5 and 6. In thismanner the heating means isrendered effective.

When the temperature of the space wherein the thermostat 68 is locatedrises then the bimetallic 55 member moves to the-right, i-lrst removingthe short circuit across the relay formed by conductors 'il yand T8 andthen into engagement with its associated right hand contact. Thereuponrelay 6l will be energized by closure of a circuit 60 leading from thesecondary of transformer 56 through conductor i9, bimetallic, member 68,conductor 1l, relay 6l and conductor back to the secondary winding.Energization of the relay causes upward movement of its associated arma-65 ture and the establishment of a holding circuit for the relay throughelectrical connection 8|- and switch member 59. Simultaneously, switchmember 79 is moved upwardly to close a circuit for the relay controllingthe operation of the 70 compressor motor` 22 of the refrigeratingappaatus. This circuit leads from one side of the transformer windingthrough electrical connection 'Hg switch 10, conductor 82 to thesolenoid 83 and from thence back to the secondary vwind'- 75 ing throughconductor 16. Upon energization of relay 83, its associated armature andswitch member 84 are moved upward to connect compressor motor 22directly across supply lines 45.

The operation of my system as a whole will now be described. For purposeof illustration I shall assume that it is desirable to maintain aminimum temperature of 70 within the spaces 33 and 34 in winter and thata maximum temperature of 80 is desirable in summer. Therefore,temperature responsive means 39 is arranged to move to the right intoengagement with its right or low contact at a temperature of 70 andthermostat 40 arranged to move into engagement with its left hand orhigh contact at a temperature of 80. It should be understood that thesevalues are merely chosen for` purpose of illustration and that thethermal responsive means may be calibrated to operate at any desiredtemperatures. It will be assumed also that the thermostats will operatewith a temperature diierential of .2 for purpose of illustration, but itis to be understood that this differential may diier in accordance withthe characteristics of various thermostats. Consequently, thediierential might be decreased to such a point that the thermostat mightbe considered as operable from one contact to the other at a particularvalue of temperature such, for example, as 70 or 80.

It will be noted -that if itis desirable to maintain a temperature ot"70indoors in winter `the heating means of the air conditioning system mustbe placed in operation sometime prior to the time that a temperature of70 obtains withinfthe space and for thesame reasons the cooling systemmust be placed in operation prior to the time that the temperaturewithin the space to be conditioned rises to 80. For this reason thermalresponsive means 68l controlling the 'cooling and heating means of theair conditioner. may be so selected that it will operate at atemperature of approximately That is, if the temperature is below 75. itwill be in the position illustrated wherein the heating means is inoperation and if the temperature is above 75 it will move to the rightand energize the relay 83 controlling the operation of the coolingmeans.

Assuming that the temperature within spaces 33 and 34 is 73 and that thetemperature outside' said space and to which thermal responsive element68 is responsive is also 73, then the various parts of the system willbe in thevposition illustrated in Fig. l of the drawing. Consequently,dampers 35 are in their closed position as relay 41 is deenergized andheating medium is supplied to the conditioner due to @e energization ofsolenoid 14. If the temperature within the space 34 decreases to a valuebelow 70, then thermostat 39 will move into engagement with its righthandor low contact thereby closing an energizing circu'it for relay 41through conductors 46, relay 41, conductor 48, thermal responsiveelement 39 and conductor 43.- Energization of relay 41 eiiects upwardmovement of its armature establishinga holding circuit for itself byclosure of contacts 49 and 50 by bridging member 5I. Simultaneouslytherewith, switch member 55 is movedintoengagement with contact 56 thuseiecting energization of motor 53 and'causing actuation of damper 35 toits open position in a` manner that has been vheretofore described.Heated air is then supplied to space 34 through ducts 30 and 32.

'I'he supply of heated air is continued until such time asthetemperatureof the space increases to ausbau differential of 2 is necessary tooperate the thermostat) whereupon thermostat 39 moves to the left intoengagement with its left hand or high contact to short circuit relay 41through conductors 46, 4| and 48 in` series with thermal responsiveelements 39 and 40. The resultant deenergization-of relay 41 effectsdownward movement of its associated armature and switch members 5| and52, the former opening'the relay holding circuit and thelatter engagingcontact 55 to c lose an energizing circuit for motor 53 which in amanner described above. I

The above operation is repeated if the temperature within the' spaceagain falls below 70.

Howeven if the temperature rises to a value above then thermostat 39will be in engagement with its left contact and thermostat 40 will moveinto engagement with its left contact to close an energizing circuit forthe relay 41 and the latter in turn will effect energization of motor 53to actuate the damper 35 into its open position.

The above mentioned assumed increase in temperature would also causeactuation of thermostat' -former. Energization of the relay effectsclosure of the relay holding circuit and also closure of the circuitcontrolling the energization of relay 83,

the latter circuit extending from the transformer through conductor 1|,switch member 10, conductor 82, relay 83 and conductor 16 back to thesecondary of the transformer. In this manner theY steam valve I6 isreturned to its closed position by the deenergization of solenoid 14 andthe ,cooled air will continue until such time asthe temperature withinthe space decreases to a value below '78 whereupon the relay 41 is shortc ircuitedwith the result that switch member 52 engages contact 55 toagain energize motor 53 to actuate the damper to its closed position.

To provide against the possibility of operation l of both thermalresponsive elements in the same range the thermostatic device may beconstructed after the manner shown in Figs. `2 and 3. In Fig. 2 thedevice is shown mounted on a suitable base 85 made of insulatingmaterial. The base is proturn actuates damper 35 toits closed positionin vided with a pair of xed supports 86 on which the thermal responsiveelements 39 and 40 are mounted. The latter are mounted as in Fig. l,that is, they are adapted to move to the right in response to a decreasein temperature and vice versa.

On the base are a second pair of supports`81 carrying adjusting means 88and 89. These are provided with right hand screws and rotation of theformer in a clockwise direction serves to increase the temperature rangein which thermoj stat 39 operates while rotation of the latter in aclockwise direction servesI to decrease the temperature range in whichthermostat 40 operates.

-Before describing the details of the means provided for preventingoverlapping of the control I shall describe brieiiy the circuitconnections. 'I'hese are exactly the same as illustrated in Fig. 1

. been labeled with reference numerals 90 and @l and the high contactshave been labeled 02 and 83.

The adjusting means 88 and 89 have been provided with a pair ofinterengaging arms 86 and respectively, to prevent the adjustment of thethermostats to operate inthe same temperature range. These arms limitthe relative rotation of the adjusting elements.

In operation, it will be apparent from an inspection of Figs. 2 and 3,that rotation of members 88 and 88 in a clockwise direction, asindicated by the arrows, serves to raise the range of operation ofthermostat 39 and to lower the range of operation of thermostat 40. Themembers 8B and 89 are illustrated as adjusted at '70 and 80,respectively, and it is apparent that they cannot be adjusted tooperateI at temperatures nearer than 10 as their rotation to operate atnearer ranges is restricted by members 913 and 95. `Obviously this rangemay be decreased or increased as desired.

'I'he system described is adapted to various modifications and itsadvantages will be clearly apparent to those skilled in the art. It isobvious that various types of conditioning systems and damper operatingmeans may be used and, in fact, that the ow of heat exchange medium maybe through various types of ducts or pipes ,and under the control ofregulating devices such as valves. I t is to be understood that myinvention in its broader aspects covers these modications as well as theone specifically illustrated.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, regulating means for controlling the flow of a heatexchange medium, means for actuating ysaid regulating means, meansincluding two thermal responsive devices each having associatedtherewith a high and low contact controlling the operation of said lastnamed means for effecting operation of the latter in a single directionin response to variations in temperature in two directions, the yirst ofsaid devices controlling said actuating means when the secondl is inengagement with its low contact, and the second controlling saidactuating means when the first is in engagement with its high contact. i

2. In combination, a control device, an energizing circuit therefor, adeenergizing circuit therefor, means for closing said energizing circuitwhen the temperature decreases below the lower limit of a rst range orincreases above the upper limit of a second range and for closing saiddeenergizing circuit when the temperature increases above the upperlimit of said nrst mentioned range or decreases below the lower limit ofthe second mentioned range, said means including two thermal responsivemeans each oper.`

able from one control position to another within one of the abovementioned ranges, the thermal responsive means operable at the lowerrange beingadapted directly to close said energizing circuit and toclose said deenergizing circuit through the second 'thermal responsivemeans, and the second thermal responsive rneansbeing adapted to closeboth said circuits only when in series with said rst thermal responsivemeans.

3. In combination, an electrical control device,

a source of energy therefonan energizing circuit therefor, adeenergizing circuit therefor, means aieaces including two thermalresponsive elements each having associated therewith a high and lowcontact for controlling said circuits, an electrical connection betweenthe low contact of one with the high contact of the second, a connectionleading from said last mentioned connection to the source of energy, aconnection from the high contact associated with said first element tothe second element, a connection from the low contact of the second tothe source of energy, and electrical connections leading fromsaid-control device to the source of energy and last-mentioned contactand to the rst element, whereby said control device is energized whensaid rst element is in contact with its low contact and when both saidelements are in contact with their high contacts, and deenergized whenthe first is in contact with its high contact and the second with itslow Contact.

4. In' a temperature regulating system, the combination of means forcontrolling the flow of heat exchange medium, and control means thereforincluding a pair of thermostats having series control connections forjointlyieiecting operation of said iiow control means to decrease the owof heat exchange medium when the temperature to be regulated is within alimited range, the control connection of each thermostat being renderedeffective at a corresponding limit of said range and each of saidthermostats having another control connection for effecting operation ofsaid flow control means to increase' the iiow of heat exchange medium inresponse to variation of the temperature beyond the corresponding limitof said range.

5. In combination, a pair of separately operable thermostatic switchesone operable from one circuit closing position to another circuitclosing position upon a decrease in temperature below a predeterminedlower limit and the other operable from one circuit closing position toanother circuit closing position upon an increase in temperature above apredetermined upper limit, and an electrical control device having onecontrol circuit connected to be closed jointly by said pair ofthermostatic switches in said one circuit closing position thereof andhaving another circuit connected to be closed upon the separateoperation of either of said thermostatic switches to the said othercircuit closing position thereof.

6. In combination, electrically operated means for regulating the flowof heating and cooling medium and having one circuit for decreasing theflow upon closure thereof and another circuit for increasing the ow uponclosure thereof, means for closing said one circuit including a heatingcontrol thermostat operable from one position to another position uponan increase in temperature above a predetermined lower limit andl acooling control thermostat operable from one position to anotherposition upon a decrease in temperature below a predetermined upperlimit, said heating and cooling control thermostats being connected inseries to close said one circuit in said other positions thereof,connections whereby said heating control thermostat closes said othercircuit upon operation thereof to said oneposition.

thereof independently of said cooling control thermostat, andconnections whereby said cooling HARRY RCRAGO.-

